Into the belly of the beast! In the second chamber there is nothing much to look at, except that the walls are decorated with cheerful little paintings, no larger than the illustrations of a book, each suggesting what is on the other side of the wall. One depicts a ditch full of gleaming spikes, another show a darkness filled with gleaming, waiting eyes. Another one shows a group of people climbing over easily, only to find that their flesh is melting from their bones, due to some magic or poison covering the obstacle. Feel free to find more of them, the message is simply that something nasty waits on the other side.
Obviously the way forward is over the wall, and the way over the wall is...well in any way the characters can think of. The wall is smooth stone, no individual stones or cracks visible to find purchase on, neither is it possible to penetrate its surface - knives and swords would break. It is about 6’5 foot high, so a tall person might be able to get his fingers onto the edge, but have a very hard time lifting himself up. Grappling hooks wouldn’t find purchase. Questions?